It's a close call, but my vote is that the fiscal consolidation is going to be too deep and too fast (in reality, it's only just beginning).
It's not a classic Keynesian problem because there are also some deep-seated structural problems that need to be solved in the medium- to long-term, including the fiscal implications of an aging population. And this is not the kind of recession that represents a blip on a long-run upward growth trend: we are not going to return to the previous trend growth rate (which anyway was probably an illusion), so belt tightening is inevitable at some point.
Issues are being muddled in the debate as well. As Stone indicates, if there are efficiency savings to be made these should be made anyway, irrespective of whether there is a need to rein in the deficit. Changing the mix of outputs to get a better outcomes should also be ongoing irrespective of the fiscals stance (see recent discussions on the 'War on Drugs' for example) Wasting money is not really a sensible way to sustain demand! This is different from changing service output and quality in order to make savings.
The Government is still able to borrow at 2-4% depending on the term and the private sector is saving like mad. Monetary policy seems to be rather ineffective. These seem like the conditions for a Keynesian demand-side boost. Probably national insurance was increased too soon and VAT should not have been pushed up to 20% at the beginning of this year (there is evidence that the previous small cut in VAT did have a significant stimulus effect). Is there any evidence that the markets were really ready to punish the UK for not adopting a very restrictive fiscal policy? Not much, I would say.
In reality, the squeeze on expenditure might turn out to be somewhat less severe than at first planned as the political dimension plays out. Look for example at the current discussion surrounding the plans for cutting Justice Department expenditures by 25%. Gaffs aside, Ken Clarke is trying to be innovative, but coming up against the law-and-order camp of his party.